In Patent Document 1, as illustrated in FIG. 17, there is disclosed a piezoelectric power generator having a cantilever structure in which one end of a power-generating element 100 is fixed to a fixing member 101 and a weight 102 is attached to the other end of the power-generating element 100, which is a free end. The power-generating element 100 is formed by piezoelectric bodies 104 and 105 being adhered to the two surfaces of a metal plate 103, and, when the power-generating element 100 is seen from above, the power-generating element 100 has the shape of an isosceles triangle whose width gradually becomes narrower from the fixed end to the free end. In this case, a bending stress applied to the power-generating element 100 can be made uniform in the length direction and therefore the power-generating element 100 can generate charge substantially uniformly along its entire length and the power-generating efficiency can be improved compared to the case in which a rectangular power-generating element is used.
Incidentally, there are power generators that are used in a vibrational range of comparatively low frequencies, such as power generators that for example utilize the vibration that occurs when a person is walking or the vibration of a bicycle or an automobile. If the natural frequency of the power-generating element is made to be close to the frequency of such a low-frequency external vibration, the power-generating element can be caused to resonate and the amount of power generated is increased. The generated amount of power P of a power-generating element is determined by a constant A, which is determined by the piezoelectric material that forms the piezoelectric body, a stress σ applied to the piezoelectric body and the volume V of the piezoelectric body as expressed by the following equation.P=A×σ2×V 
However, if only a single power-generating element 100 is used as in Patent Document 1, there is not likely to be a large increase in the amount of generated power. If the length of the power-generating element is increased, the stress is increased and therefore it is possible to increase the amount of power generated with even a single element, but this opposes size reduction.
In Patent Document 2, a piezoelectric power generator is disclosed in which a plurality of power-generating elements having different resonant frequencies are supported in a cantilever manner. This piezoelectric power generator, as illustrated in FIG. 18, includes a plurality of power-generating elements 201 to 203, which each have one end fixed to a base portion 200 and another end acting as a free end, and weights 204 to 206, which are attached to the free ends of the power-generating elements 201 to 203, and the lengths of the power-generating elements 201 to 203 are different from one another. In this piezoelectric power generator, the resonant frequencies of the individual power-generating elements are made to be different from each other in order to generate power over a wide range of frequencies, but it is possible to increase the amount of power generated at a particular frequency if the resonant frequencies of the individual power-generating elements are made to be the same as each other. However, the plurality of power-generating elements 201 to 203 are arranged parallel to one another and therefore a large amount of space is occupied and the power generator cannot be formed with a small size.
Patent Document 1: Japanese Unexamined Patent Application Publication No. 11-136964
Patent Document 2: Japanese Unexamined Patent Application Publication No. 7-245970